Broadband wireless networks based on various standards (e.g., Institute of Electronic and Electric Engineers (IEEE) 802.16 based WiMAX standard and its evolution to IEEE 802.16m provides various types of services such as voice, packet data and so on. In order to provide these kinds of services, control information and data packets needs to be exchanged between a transmitting device and a receiving device. In downlink scenario, the transmitting device may include a base station and the receiving device may include a mobile station. In uplink scenario, the transmitting device may include a mobile station and the receiving device may include a base station.
Typically, service data is generated by various applications running at the transmitting device for providing various types of services. The service data is then exchanged between the transmitting device and the receiving device upon establishing a connection. Generally, the connection is identified by a connection identifier.
Multiple connections may exist between the transmitting device and the receiving device to carry service user data belonging to multiple applications running at the transmitting device and the receiving device. On the contrary, a single connection may also be used to carry the service user data belonging to multiple applications running at the transmitting device and the receiving device. Each connection carries variable size MAC Service Data Units (SDUs) received from various applications and contains service user data.
Typically, the transmitting device generates MAC PDUs from one or more MAC SDUs and transmits the MAC PDUs in physical burst to the receiving device over a wireless network. Each MAC PDU generally consists of a MAC header and a payload. In case fragmentation is enabled, payload of each MAC PDU contains a fragmented MAC SDU. In case fragmentation is not enabled, payload of each MAC PDU contains one or more unfragmented MAC SDUs, each unfragmented MAC SDU having size equal to a negotiated maximum size as depicted in FIG. 1. A negotiated maximum size is a maximum size of MAC SDU that a MAC layer can receive from an upper protocol for transmitting the MAC SDU on a MAC layer connection. The negotiated maximum size enables the receiving device to determine whether payload of received MAC PDU contains single or multiple MAC SDUs during unpacking of the MAC PDU.
The negotiated maximum size generally depends on size of application and its throughput requirements, Maximum Transmission Unit (MTU) of the broadband wireless network, whether security is applied by MAC layer on MAC layer connection, whether security algorithm is independently applied on each MAC SDU or each payload containing one or more MAC SDUs and/or other fixed information added to MAC SDUs for generating MAC PDU(s).
Typically, negotiated maximum size of a MAC SDU that the MAC layer can receive from upper protocol layers for transmission on the MAC layer connection is preset by a network entity (e.g., a base station) for all connections. However, the preset negotiated maximum size can be altered by the transmitting device independently for one or more connections when size of data packets for an application is switched, a new application is mapped to a connection, or MTU of the broadband wireless network is changed. However, the receiving device may not be in sync with the transmitting device during change in the preset negotiated maximum size. As a consequence, the receiving device continues decoding the received MAC PDUs using the previous negotiated maximum size, leading to failure to decode the MAC PDUs carrying unfragmented MAC SDUs with size equal to the new negotiated maximum size.